Wednesday, March 12, 2014

I happened to see a Chilton's Repair Guide for the Kaypro -- yes, THAT Chilon's -- and thought it might be a nice-to-have. So after casting about at the usual sites, I came up with this:

Amazon

An on-line book store

A thrift store in Washington State

Can you believe the first two? $800 plus and $600 plus? I thought maybe it's an exhaustive compendium of dark secrets, right?

So when I saw one available at the Washington state thrift shop for bout $2.00, I jumped on it. Even went for expedited shipping for a total of less than $10 delivered.

Ten days later (so much for the $8.00 speed-up mailing), it arrived and I pored over it. What a waste! I knew more than most of the stuff in there! My main interest was in the guts of the video board and principally why the display was skewed. (Please read the posts below to see what I am talking about.) The book had only FOUR pages on video boards -- two pictures, three diagrams (not including the Micrex board), and 50% of the verbiage was "there are lethal voltages running around there and you're too stupid to understand this shit anyways. Get your ass over to a professional and let him adjust the variable pots for you."

That's it!

Nuts! I am sure glad I was not rebuilding a truck transmissions; they'd probably tell me how to start the diesel and give me directions to the local GM or Ford dealer.

Oh yeah, they did have some trouble-shooting tips. You know, like

Main board does not function....Replace main board
No power........................Plug in computer
................................or replace power supply
Floppies do no spin.............Replace floppies
..etc.

A sense of tranquility fell over the workshop late this evening. My son, the Good Lance Corporal, dragged his Suzie (Suzuki motorcyle) into the garage for some minor clean-up and we hung out as I applied the finishing touches on the Kaypro -- paying particular attention to straightening the wiggles near the bottom of the display.

This time, I tweaked the controls and noted that the was some interaction like the tech manual said. I got it petty close but could not eliminate the pronounced skew on the bottom right of the display top disappear. "Close enough for government work," comes to mind.

I also took some time to lash the new phone jack connector to the old keyboard plug and mount that. So, I'd say the old girl is about 80% I am getting some intermittent problems with getting disks to boot. Is it a symptom of the problem I encountered last Sunday? Dunno? But it would be kinda neat if I could mate this unit up with the FreHD that is being kluged into TRS-80s Mark IVs. I remember I one had an MD-DOS board inside the 2x and seeing there was little or no advantage to DOS V2.11 over CP/M, I used it as a ram disk.

Old broken phone jack and new replacement.

View of the old plug and the new phone jack with spiffy repair.

Finally wedged snugly in place.

The 2X with a slightly better editor and something better than the ECO-C compiler I was trying out tonight would be half interesting. Wonder how I can do that? Hmmmmmmmmm!

Anyway, it's back on the shelf, waiting like a good and faithful servant for the FreHD stuff to come along.

Monday, March 10, 2014

After a fun-filled weekend, my old Kaypro 2X is back on the air -- sort of. The Micrex video board was re-capped and that seemed to have resolved the problem. At that point, I was a little disappointed that my quest was so easily fulfilled. It was a real no-brainer to buy some capacitors, wick out the old ones and replace them, turn it on and view the results. Moderately plain sailing.

Or so I thought.

Anyway, by way of passing on what I'd learned here's a summary of some notes I made to help others traveling along this road. Below are the initial pictures that tell the tale:

Bad K2X Display Symptoms

Captioned Micrex TW-105 94V-0 Board

Final "Semi-Fixed" Display

List of Micrex Board Electrolytic Caps

As I said, it did not turn out to be as smooth a journey as I thought it would be. After routine checkout on the bench, the reassembly turned into a nightmare. The disk drives would not boot, not spin, and and generally became non-responsive. I did a little snooping around the board and found that all the chips had the proper Vdd (+5V), the power connector yielded the proper voltages to the main board (-11V, +12V, +5V) and the drives.

I even checked a couple of signals on the board:

1 MHz Signal at pins 2, 4, and 5 of U65

2.0 MHz signal at pin 13 of u65

These weren't the only signals I scarpered. Just too busy head scratching and trouble-shooting to make a proper documentary suite of it. When things get squared away, I will revisit this and do shots for a good machine as a reference for any others wishing to revive Kaypros. (You listening, Vintage Computer moderators?)

Eventually, I determined all was working on the main board and, after testing the floppy ribbon cable and connectors, wiped down the floppy edge connector with a Q-tip and alcohol. Seems to have worked because the old girl sprang to life and booted!

I still have two problems with the video, however. (1) It's not centered vertically and (2) It's a little skewed on the bottom (see below). It may be due the the fact that I did not replace the 4.7 uF non-polarized cap; the guy at the store pulled a weensie polarized one when I was not paying attention. So, I'll get a proper cap for that and see what it does.

Wavy Gravy at work on the bottom quarter of the screen

But the vertical thing has got me buggered. There is only a "V SIZE" (V405) control and a "V LIN" control (V410) and right now, the "V SIZE" is at full throttle. The instructions in the Kapro technical manual (Jun 1985 edition) says this:

I was pretty tired Sunday afternoon but I seem to remember doing just that only it did not seem to yield the desired results. I may not have gone back and did a "dip the plate, peak the load" procedure (just like my old TS-830s) ao I'll tinker with it some more and see it that fixes it.

Another matter that needs resolution is the keyboard jack. My old one fractured and I was casting about for a replacement scheme. I had seen some folks' kluges on the Internet -- one literally looked as though the guy chewed up a wad of Double Bubble and used that to join the broken cable to the plug. (I still do not comprehend folks restoring stuff like this who will not make a proper investment in a solder station and associated education in the skill.)

I ran this by my wizard friend, John, "the knower of all things", and he pointed out a similar part to the shredded female jack in the picture above. Finally tracked it down at Digikey who got it out to me right away. I will Hoover up the order and PN info and add it if I do a post on the keyboard repair job.

Until then, it's back to the UW project and twiddling the video board pots to see if I can exorcise Wavy Gravy.

Friday, March 7, 2014

My Tek 7704A lives! It was revived by the gentlemen who provided me with it originally. Read here the colorful background on just how this came to be.

One has few true friends in his lifetime. Some become friends at work or in a sport that one indulges in or as a fellow member of a club or organization or by way of a hobby or pastime.

Dick, WB6JDH, is a true friend and a person who I crossed paths with because of our mutual love of Amateur Radio. I'd say "electronics" but that's not really the truth in my case; I am still one of those wriggling things, clambering up onto the sand, trying to extricate myself from the primordial ooze. Dick has long since deposited himself well inland, evolved through the lizard, early mammal, Neanderthal and Cro-Magnon stages, and walks erect into the sunny uplands of electronic theory.

I stand in awe of him -- not only because he knows shit but because he does shit. He crafts radios, test equipment, devices, restores the old and preserves it for the rest of us -- the largely great unwashed -- who have little or no appreciation for this art, its attendant skills, or the worth of beautiful things from the days gone by.

During his career, he was a chemist -- a graduate of San Jose State back in the early 60s -- who stood many hours at vats of printer's ink formulating the ingredients of one color or another. Somewhere along the line he took up flying model airplanes (held a control-line speed record I am told) and gardening (he and his lovely wife, Ann, are constantly pruning, weeding, manicuring the vegetation that surrounds their ancestral manse, The Groveside Arms). He also dove into ham radio. Maybe the intellect that allowed him to master the arcane art of chemistry also gave him the talent to understand electronics but I more think it is his temperament and tenaciousness. When faced with a problem, He is like a terrier, unrelenting until he understands the underlying concepts and principles and then doggedly pursuing the resolution.

His domain, his kingdom is the workshop in his garage. Of course, it long ago lost the capability to house both of his cars. Rather, it became a magic repository of the miraculous electronic detritus; radios and instruments and fragments from the stone age to the near-past. He probably has two of everything except for those items he has three or more of.

Over the last decade, Dick has ventured into the arcane world of repairing old oscilloscopes, specializing in old 70s and 80s Tektronix and Hewlett Packards. As the picture above shows, he has a stack of Tek 7704s and 7904s, a quintillion plug-ins, and various and sundry other related gear. In addition to that, he has a storehouse in the backyard housing even more treasures as well as what I call his "knob farm" -- dead Tek 465s and 7704s that he cannibalizes parts from and uses to plant geraniums.

To me it's all like that wonderful scene in the 50s move "King Solomon's Mines" where Steward Granger stumbles into the cavern strewn with jewels and gold and silver and any trinket imaginable.

But this treasure trove grows with each two-per-month visit to the Southern California swap meets, gracious attendance to fellow ham's estate sales, local salvage emporiums, and general ham-to-ham barter. And, as I said above, he often finds his inventory augmented by repair drop-offs.

And now to the reason for this post: About two years ago, I had been visiting Dick on a regular basis only to realize I had been subjected to a constant mantra by Dick to the effect that I really needed to upgrade my bench scope to something like a 7704. He was semi-kidding, of course, but it became more intense during late one rainy February when I had made several trips to his Mecca in a vain attempt to repair my wavering Tek 2465. (I thought I did a post on that but cannot find it.) In any event, I was troubleshooting the beast and located a bad resistor which breathed life into it again. But, alas, the 2465 was crippled and maimed and actually no longer serviceable. It was at that point I succumbed. Dick and I chatted and negotiated and -- in return for the remains of the 2465 and a very reasonable amount of spare cash, I was "lent" one of the 7704s from his stack and four very useful plug-ins.

Of course, I got it back home and, for the life of me, could not figure out where to put it on the bench. But setting it up and operating it got me hooked and I never looked back. Eventually, I hollowed out a spot for it (see picture above and some previous posts with pictures of my bench) and revel in its complexity, accuracy, and beauty. It has performed reasonably faithfully barring a couple of incidents with a misbehaving 7CT1N curve racer and a 7D15 frequency counter.

Dick and I pored over the curve tracer and sort of mutually solved. Well, Dick did most of the brain work and I did the donkey tasks. But I felt pretty good just to have taken a part. The counter was a more formidable problem and I am justifiably proud that I solved this one myself. (If you do not count the advice I got from the guys on the Tek Scope Yahoo group. From thence, I thought, I was off and running.

Or so I thought.

During my effort to get the UW VFO working, my Tek 7704 lost the trace and no amount of pushing buttons replacing plug-ins or hurling invectives would restore it. So, in a frenzy, Dick got a call and a desciption of the situation. He graciously set aside some of his Friday afternoon for me to visit. He also said that he had a couple of 7904s ripening on the vine and maybe I would be interested. I owned that I would (thinking that Dick would countenance a swap) and made arrangements to take Friday afternoon off from work.

Long story even longer, I showed up and we poked and prodded and measured and scratched our heads to no avail. Dick verified that the mainframe power supply voltages were present and correct and we pressed on. After a bit more of this confusion, Dick blithely reached over and turned the left side mainframe intensity control clockwise and -- BAM! -- let there be light!

Now didn't I feel the fool? It was one of those humbling experiences that embarrassed me but not that much because I got to spend the afternoon with a good and dear friend.

The trade for the 7904? Well, truthfully, I was so glad to have my old 7704A back with me. It had served me well over the past couple of years and I would have felt like I was selling one of my children into slavery had I parted with it. So, I loaded it up into the back of the Jeep and joyously returned to the shack on another rainy February day..

Tuesday, March 4, 2014

I diddled with the KayPro some over the weekend and have been led to believe that re-capping the Micrex video board might solve my problem. I will do a more lengthy post on that as reference in the event anyone's searching. But, honestly, my impression of the knowledge out thee on the various Retro Computing boards is miles wide and millimeters thick. I sure as hell ain't no double-E but some of the folk lore is just absolute fantasy land presided over by witch doctors. I'll dig up some of the incredible excerpts when I do my post. One of them is a real side-splitter.

Anyway, I had a few moments this evening and wanted to engage in some idiocy of my own, so I turned back to the Ugly Weekender VFO. What follows is something that outstrips the stupidity of the KayPro posts and leaves them panting in the dust!

You are warned!

I put it in the form of an e-mail to WB6JDH:

Dick,

Per your advice, I rewound the coil: 42 turns tapped about 10 turns up from ground. It measured out at 8.45 uH and, when strapped in alone without the variable cap, hummed along at about 4.810 MHz. Adding the variable cap dropped it to 4.700-4.780 MHz (swinging the cap). Here are some pictures:

Source of Q1

From there:

Collector of Q3

No wonder we use a transformer after Q3. How does it eliminate all of that hash?

Output of T1

Note that I swapped the 10K resistor for a 5K and that only gave me the 650 mV above. When the 10K was swapped back in, it rose a bit. I still don't understand why that stage is in there unless it's to buffer the VFO from the next stages.

Anyway, I lashed in the variable cap and just for grins measured the total capacitance across C2 (i.e., the entire L/C circuit) and got a 180-270 pF swing across the range of C1.

Probably not kosher; tracing that out on the nomograph yields about 3.200 MHz.

If I do some rough calculations, the two caps in parallel yield 100+10 pF to 100+120 pF or a range of 33-39 pF. That in parallel with the 100 adjacent to C2 (which is not in the circuit) yields 133-139 pF, I guess. Probably wrong; maybe not. Look what it does on the nomograph:

Using the nomograph again, I gotta wind a toroid a little less that 4 uH to get the VFO in the 7.000-7.070 MHz range. That's about half of what the coil is no (42 turns) -- or 21 turns.

Not really sure what will happen if I don't land on 7.000 MHz going up -- So I am going take a deep a breath and probably add a padder at C1 and see what that that does and *then* rewind the toroid. That way I can zero he VFO in.